1. Field of the Invention
The invention relates to a method for polymerizing alpha-olefins, a catalyst for such a polymerization method and a method for producing such a catalyst. More particularly, the invention relates to a catalyst and to a method of using thereof in alpha-olefin polymerization reactions which produces linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) having high bulk density. The invention also relates to a catalyst composition exhibiting very high productivity characteristics, as compared to similar prior art catalysts.
2. Description of the Prior Art
Linear low density polyethylene polymers possess properties which distinguish them from other polyethylene polymers, such as homopolymers of polyethylene. Certain of these properties are described in Anderson et al., U.S. Pat. No. 4,076,698.
Karol et al., U.S. Pat. No. 4,302,566, describes a process for producing certain linear low density polyethylene polymers in a gas phase, fluid bed reactor.
Graff, U.S. Pat. No. 4,173,547, Stevens et al., U.S. Pat. No. 3,787,384, Strobel et al., U.S. Pat. No. 4,148,754, and Ziegler, deceased, et al., U.S. Pat. No. 4,063,009, each describe various polymerization processes suitable for producing forms of polyethylene other than linear low density polyethylene, per se.
Graff, U.S. Pat. No. 4,173,547, describes a supported catalyst obtained by treating a support with both an organoaluminum compound and an organomagnesium compound followed by contacting this treated support with a tetravalent titanium compound.
Stevens et al., U.S. Pat. No. 3,787,384, and Strobel et al., U.S. Pat. No. 4,148,754, describe catalysts prepared by first reacting a support (e.g., silica containing reactive hydroxyl groups) with an organomagnesium compound (e.g., a Grignard reagent) and then combining this reacted support with a tetravalent titanium compound. According to the teachings of both of these patents, no unreacted organomagnesium compound appears to be present when the reacted support is contacted with the tetravalent titanium compound.
Ziegler, deceased, et al., U.S. Pat. No. 4,063,009, describe a catalyst which is the reaction product of an organomagnesium compound (e.g., an alkylmagnesium halide) with a tetravalent titanium compound. The reaction of the organomagnesium compound with the tetravalent titanium compound takes place in the absence of a support material.
A vanadium-containing catalyst, used in conjunction with triisobutylaluminum as a co-catalyst, is disclosed by W. L. Carrick et al in Journal of American Chemical Society, Volume 82, page 1502 (1960) and Volume 83, page 2654 (1961).
Nowlin et al., U.S. patent application Ser. No. 444,152, filed Nov. 24, 1982, now U.S. Pat. No. 4,481,301, teach an alpha-olefin polymerization catalyst prepared by heating a solid, porous carrier in a nitrogen atmosphere at a temperature of about 100.degree. C. to about 800.degree. C., contacting the carrier containing reactive hydroxyl groups (OH) with a greater than a stoichiometric amount of an organomagnesium composition, and reacting the product of that step with a tetravalent titanium compound, also used in the amount greater than the stoichiometric amount thereof with respect to the hydroxyl groups on the carrier, to produce a catalyst precursor. The catalyst precursor is then combined with an activator, also known as a co-catalyst, to produce an active catalyst composition.
It is a primary object of the present invention to provide an active catalyst composition which is capable of polymerizing alpha-olefins either in a continuous, gas phase fluid bed process or in a batch reactor process to produce polymers having increased bulk density, as compared to polymers prepared with the catalysts of prior art.
It is an additional object of the invention to provide an alpha-olefin polymerization catalyst composition having higher productivity than the catalysts of prior art.
Additional objects of the invention will become apparent to those skilled in the art from the following description of the invention.